In the operational environment of private industry and public utility, vessels or cavities are often employed, and in some instances, the only available access to those vessels or cavities is a manhole, manway, or other similar opening. These openings are employed during construction, maintenance, or inspection. Through these openings, materials, supplies, tools, and personnel pass. In some instances, loads (materials, supplies, tools, personnel) must be lifted without the benefit of a ladder or other means of traverse. In such instances where it is desired to transition the location of a load from one point to another in the vertical plain, ropes, cables, or other means are used in conjunction with various apparatuses to achieve such movement. A variety of apparatuses from simple tripods equipped with pulleys as is disclosed by Ascherin et al. in U.S. Pat. No. 6,059,266 to rather large and complicated apparatuses such as is disclosed by Daniel, III in U.S. Pat. No. 6,405,831 are employed. Many of the apparatuses available at present have certain limitations to their effectiveness. A basic tripod, such as that disclosed by Asherin et al. in U.S. Pat. No. 6,059,266 (or even bi, tri, or quadrapod as disclosed by Smith in U.S. Pat. No. 6,056,273) and pulley assembly limits access to the opening of vessels or cavities as the legs of the tripod or other device as described increasingly narrows the open field of movement as the structure reaches its high center point at the apex. Other means which provide better access by means of a single boom such as that disclosed by Stoner in U.S. Pat. No. 1,887,965 and Ostrobrod in U.S. Pat. No. 5,820,108 are bulky, awkward, and limited in employ by their size. Smaller versions such as that disclosed by McInerney in U.S. Pat. No. 4,135,627 while size and weight have been reduced are limited in the weight which can be lifted due to the means of counterbalance or lack of a means of connecting somehow to the surface upon which the apparatus is mounted. Joyce discloses in U.S. Pat. No. 4,597,562 a creative approach, but the apparatus disclosed cannot establish a variable high center point as its boom is fixed. The means of connecting to the manway or access as disclosed by Joyce is also incapable of bearing heavy loads and thereby limits use. The above disclosures are limited to applications where ingress is presented in a horizontal plane. In applications where ingress is presented in a vertical plane, these means are of no value. Willaughby discloses in U.S. Pat. No. 5,431,248 an interesting approach to vertical access. Nevertheless, the apparatus therein disclosed requires the employ of four legs and accompanying straps as well as an adjusting stabilizing arm. The legs, straps and stabilizing arm limit access and movement at the manway, and the four straps when under the force of heavy loads would stretch thereby causing the adjustable stabilizing arm to drop and further interfere with access. When Willaughhby's apparatus is employed in a horizontal application, the four legs present a hindrance to essential access.
A further limitation of the present art is the awkwardness and bulk of the apparatuses available when transporting them to the site at which the apparatuses are to be deployed as in many instances individuals must climb a vessel carrying the apparatus which is to be deployed, particularly in emergency situations.
Consequently, a need exists for improvements in the means and methods of seeking to transition the location of a load contained within vessels or cavities which are accessed by means of a manhole, manway, or other similar openings which provides for limiting peripheral interference, the establishment of a high center point in both horizontal and vertical applications, and limiting the weight and bulk of such apparatuses.